Exemplary embodiments of the present invention relate to an extreme ultraviolet lithography technology, and more particularly, to a method for fabricating a pellicle which protects an extreme ultraviolet (EUV) mask from particles.
As circuit critical dimensions (CD) of semiconductor devices have become more and more reduced, physical limitations in using ArF exposure apparatuses to achieve the requisite resolution needed in transferring fine patterns onto wafers have been reached. Accordingly, EUV lithography technology has been developed in order to transfer finer patterns onto wafers. The EUV lithograph technology is considered as a next generation technology which will be used to fabricate a slimmer and faster microchip having a critical dimension of 32 nm or less by using EUV light having about 13.5 nm exposure light wavelength.
Since EUV lithography technology uses light having a very short wavelength, a mask in which circuit patterns to be transferred onto a wafer are preferably provided in mask patterns that do not have light-transmission type structures but rather preferably have light-reflection type structures. Mask used in the EUV lithography processes are likely to include light reflection layers with a multilayer structure of Mo/Si layers on a substrate having a low thermal expansion coefficient (LTE), such as quartz, and a light absorption pattern formed on the light reflection layer that partially expose the surface of the light reflection layer.
A pellicle is often provided in order to protect the surface of the EUV mask used in the EUV lithography process from contamination sources such as particles. However, fabrication of such a pellicle that satisfies the demands of EUV lithography is difficult because, among other reasons, it is difficult to use polymers to fabricate a suitable pellicle membrane. In particular, it is well known that carbon-fluorine (C—F) based polymers absorb EUV light, and therefore it is practically difficult to use C—F based polymers as pellicle membranes. Thus, materials having high transmissivity with respect to the EUV light has been suggested as suitable candidates for pellicle membranes. For example, the following pellicle fabricating method may be employed. A mesh of a metal wire such as nickel (Ni) is formed by electroplating, and the mesh is mounted on a polymer film. Silicon (Si) is then deposited to form a silicon membrane layer. Subsequently, the polymer film is removed which results in the silicon membrane layer remaining attached to the mesh.
However since this type of pellicle fabricating method uses a polymer film as a sacrificial layer, then bubbles generated during the coating of the polymer film may arise and can result in causing defects on the silicon membrane layer which is subsequently deposited on the polymer film. Such defects may serve as factors that cause exposure defects during the EUV exposure process. Moreover, an alternate wet etch process may be performed by using organic components of the polymer during the process of removing the polymer film, however the resultant surface of the silicon membrane layer may be damaged during the wet etch process. This is accompanied by the defects on the silicon membrane. Therefore it is difficult to fabricate suitably pellicles that satisfy the demands of high resolution lithography that uses EUV.